Question 1145222
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The total distance equation is

    3r + 3*(r-20) = 306

where "r" is the value under the question.


Hence,


    3r + 3r - 60 = 306

    6r           = 306 + 60 = 366

     r                      = 366/6 = 61 mph.


<U>ANSWER</U>.  The average rate of the bus on the level road was 61 mph.
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Solved.